The present invention relates to a photoresist composition, and more particularly, to a photoresist composition which can be used for forming a black matrix pattern for a cathode ray tube by using a lithography process and which can obtain a sufficient hardening effect even in a short exposure time.
In general, in the screen of a color cathode ray tube, green, blue and red-emitting phosphor patterns are arranged regularly in a dot or stripe form. Also, in order to improve contrast and color purity of the screen, a black matrix is formed between the respective phosphor patterns. The block matrix is generally formed by using a lithography process, like in forming the phosphor patterns.
The lithography process is comprised of the steps of coating, exposing and developing the photoresist. Here, the photoresist is divided into a positive type and a negative type, which is selectively used in consideration of the required sensitivity, shape and resolution of a pattern to be formed, and coherence to a substrate.
In more detail, in the case of using a positive photoresist, a slurry of photoresist and graphite is first manufactured. Next, the slurry is coated on the inner surface of a CRT panel, a shadow mask is provided, and then the slurry is exposed and developed to form a black matrix pattern.
However, in the case of using a negative photoresist, if the same method is used as in the case of the positive photoresist, the black matrix pattern may be formed at the portion where the phosphor patterns are to be formed. Accordingly, a process different from that using a positive photoresist must be adopted for forming the black matrix pattern.
In other words, a negative photoresist composition not containing graphite is coated on the inner surface of a CRT panel and then exposed and developed to form a resin pattern at the exposed portions where the phosphor patterns are to be formed. Graphite is coated on the resin pattern formed surface and then the resin pattern is etched using sulfuric acid, thereby forming the black matrix pattern.
The negative photoresist composition contains a photo-curing polymer resin and a photosensitive agent dissolved in an organic solvent. As the photosensitive agent, one of 4,4'-diazido-2,2'-stilbenedisulfonate sodium salt (DAS) is mainly used.
The photosensitive agent is sensitive to light and functions as a cross linking agent. If the negative photoresist is coated and then light is irradiated for a predetermined time, the photoresist is hardened by the cross linking reaction of the polymer with the photosensitive agent. Here, in order to reduce the time of the lithography process, it is necessary to shorten the exposure time. For this purpose, it is necessary to develop a photoresist having excellent photo-reactivity.